本研究旨在探討新增一條捷運線對大台北地區特定車種(機車或汽車)之交通事故影響，並探討此三項交通工具之關聯性。本文使用民國93年至97年大台北地區A1、A2類道路交通事故調查表資料進行實證研究，並藉由控制相關變數，以期能更全面了解肇事率及死傷情形之影響因子。 本文以Probit概率迴歸模型及負二項迴歸模型做為實證模型，並運用差異分析法探討土城捷運通車前後對於新北市之事故發生率及死傷人數是否有改善。實證結果發現，與汽車有關的交通事故率與死傷人數確實下降，而機車有關之事故率及死傷數卻顯著增加。機車之機動性高且便於進行其他活動這是捷運所無法取代的且由於交通情形的改善亦有機會誘發更多通勤車輛的湧現及超速之現象，是故機車之肇事比增加。其他肇事特性證實酒駕肇事對於汽車有關之事故率與死傷人數有正顯著的影響，顯示視線不良、反應神經遲鈍易增加交通事故。而油價之增加對汽車有關之死傷數有負顯著的影響，但對機車卻是正顯著，顯示兩者之間有替代關係。 ;The research is to discuss the effect of adding a new MRT line towards Greater Taipei Area and its traffic incidents of motorcycles and vehicles. This dissertation is meant to further discuss and dissects the co-relations of these three types of transportations. This thesis use the data of Greater Taipei Areas’ type A1, A2 traffic accidents from the year 2004 to 2008 to provide full database figures with the independent variables in order to fully discuss the crash rate and the casualties factors. The dissertation uses probit regression model and negative binomial regression model as based models and further analysis the difference-in-difference towards the before and after effects of the new Tucheng MRT’s operation with New Taipei Districts’ traffic incidents rates. As a result, the thesis has found the vehicle related traffic incidents rate and casualties have decreased. However, the motorcycle related incident rates and the casualties have increased. The mobility and the convenience of motorcycle is irreplaceable by MRT thus the growth of the motorcycle quantity is inevitable. With the growing rate of motorcycle to vehicle incidents, the other factor such as, DUI (drink under influence) do consist the define effect cause by the blurry line of vision, and dull reflex. The increase of gasoline price leads to the negative significant to vehicle crash rate and casualties, though it illustrate the positive significant of motorcycle. It provides the positive relation of the two type of substitutable transportation type.